<html>
<head>
<script language="javascript" src="jquery-1.6.4.js"></script>
</head>

<body>

<form id="form1" name="date" method="post" action="owa.php"> 

<select name="ip_list" id="ip_list" onchange="selectedIP()" >
<option value= '' > Select IP </option>
<option value= 'test' >1</option>
</select>
<script language="javascript">
	function selectedIP(){
	
    $("#ip_list").change(function() {
    $("#login_list").attr("disabled","disabled");
    });

}
</script>

<select name="login_list" id="login_list">
<option value= '' > Select Login </option>

</select>
</form>
</body>
</html>